Question

The batteries from a certain manufacturer have a mean lifetime of 880 hours, with a standard deviation of 70 hours. Assuming that the lifetimes are normally distributed, complete the following statements.

Answer 1

Approximatley 95.4% of the batteries have lifetime between 740 hours and 1,020 hours. O = -2 O = 2

* Fall within 2 std. dev. of mean

Approximatley 68% of the batteries  have liftetimes between 810 and 950 hours.

100k for -1 & 1 std. dev.

( 810 & 950)

-1 = x-880/70   1 = x-880/70

-70 = x - 880    70 = x - 880

810 = x                   950 = x